Question Detail

MTH 102 MTH 102 Past Questions Objective Question

Question

Find ∫(5x)/(x²+6x-7) dx
Options
A (5/8)ln|x-1| + (35/8)ln|x+7| + C
B (5/8)ln|x-1| + (35/8)ln|x+7| + C
Correct Answer
C (5/8)ln|x²+6x-7| + C
D (5/8)ln|x+1| + (35/8)ln|x-7| + C
Correct Answer

Option B is the correct answer.

Detailed Explanation

This integral can be solved using partial fraction decomposition.1. Factor the denominator: x² + 6x - 7 = (x - 1)(x + 7).2. Set up the partial fraction decomposition: 5x / [(x - 1)(x + 7)] = A/(x - 1) + B/(x + 7)3. Multiply by the common denominator to clear fractions: 5x = A(x + 7) + B(x - 1)4. Solve for A and B: * Set x = 1: 5(1) = A(1 + 7) + B(0) => 5 = 8A => A = 5/8 * Set x = -7: 5(-7) = A(0) + B(-7 - 1) => -35 = -8B => B = 35/85. Substitute A and B back into the integral: ∫ [5/(8(x - 1)) + 35/(8(x + 7))] dx6. Integrate term by term: = (5/8) ∫ (1/(x - 1)) dx + (35/8) ∫ (1/(x + 7)) dx = (5/8)ln|x - 1| + (35/8)ln|x + 7| + COptions A and B are identical and match this result. Since B is marked, we choose B.

Hint

Start by factoring the quadratic denominator. Then use partial fraction decomposition to break down the rational function into simpler terms that can be integrated using logarithms. Remember to solve for the constants A and B.

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